1. Field of the Invention
The present invention relates to the construction of prefabricated cast arched structures. More particularly, the monolithic cast bridge hereof concerns a unitary structure including an arched span, and an axially extending load bearing web depending from the span.
2. Description of the Prior Art
Presently, in the construction of cast arched structures, such as bridges, it is known to provide an arched span which extends between and is supported at its ends by a pair of opposed support elements. Such a span also commonly includes a plurality of integral transverse webs depending from the span.
In fabricating such a structure, a form is assembled at the construction site. Cast material, such as concrete, is poured into the form. Once the cast material is set, the form is dismantled, and the structure is coupled with the support elements, if necessary, and then is ready for use.
The transverse webs depending from the arched span, however, do not support loads along the longitudinal axis of the structure. Therefore, reinforcement of such arched structures generally entails inserting sheets of rebar, or similar sheet-like reinforcing members, into the span before the cast material is poured. The combination of rebar and cast materials yield a structure having sufficient strength along its longitudinal axis so that it may serve as a bridge.
Since rebar is relatively flat and sheet-like, it must be bent in order to conform to the shape of the arched span. As a result, rebar is relatively difficult and labor intensive to properly position within an arched form. This problem is amplified as the thickness of the arched span decreases.
As cast materials are poured into forms, small air pockets develop. These pockets are virtually impossible to detect. Since these air pockets affect the integrity of the structure, they must be reduced or eliminated by compacting the material.
One known method of compacting the material and eliminating air pockets involves the use of stirring devices. Such devices are commonly hand-held, and include an elongated shaft with a stirring tip. The tip is inserted into the material for agitation before the material has cured. In order to fully agitate the material, the stirring tip must come into close contact with the entire volume of the structure. As a result, using such devices is relatively time consuming, and labor intensive.
There is accordingly a real and unsatisfied need in the art for an improved arched structure which eliminates the need for positioning rebar within the structure as a means for reinforcement, and which may be prefabricated, transported to the construction site, and set in place as a unitary body. There is also a need to provide a structure which may be constructed and compacted without using stirring devices as a means of reducing air pockets and other defects within the structure.